This invention relates to a vehicle-loaded display device adapted to indicate various numeral information, image information, etc. on a two-dimensional display, and more particularly to a vehicle-loaded display device in which a two-dimensional display is arranged on a steering wheel allowing the driver to see its screen easily.
In vehicles, a steering wheel is positioned nearest to the driver, more specifically to his hands. For the purpose of improving the operability, therefore, a control board equipped with key switches or so for instructing the control of vehicle-loaded apparatus and units, indicators, etc. are preferably mounted at the central portion of the steering wheel.
Further, two-dimensional displays such as a Braun tube type display (CRT) are preferable to be used as an indicator when indicating a large quantity of information or image information. In general, however, since there are arranged a number of apparatus and units in the vicinity of the driver's seat, it is difficult to secure a large space there for the purpose of indication. Accordingly, small-sized displays must be used in such case. But, the reduction in size of the used display makes it harder to see the information indicated on the screen, so that the display is preferably arranged on a steering wheel which locates near the driver. On the other hand, since the available space on the steering wheel is also limited, there can be mounted thereon no more than the minimum constituent members such as key switches and a two-dimensional display.
With the arrangement as mentioned above, in spite of such a need that a large quantity of information must be transmitted between a steering control board and the vehicle body side, a steering mechanism for transmitting rotation of the steering wheel to a steering shaft has a complicated structure, and this results in difficulty in writing for the power supply and the signal cables used to connect a control board mounted at the center of the steering wheel (i.e., steering control board) with a stationary control unit. An interconnection mechanism comprising a combination of slip rings and brushes can be employed in order to effect the wiring without causing any obstruction against rotation of the steering wheel, but a larger number of slip rings and brushes are required for transmitting a larger variety of information. This causes the interconnection mechanism to be complicated in its structure and to require a wider space for its installation. As a result, such wiring will be confronted with a substantial difficulty particularly in the steering mechanism which has a strictly limited space available thereto.